Method of the manufacture of an implantable intraocular planar/convex, biconvex, planar/convex or convex/concave lens, an open mold used for the execution of this method, and a lens made using this method

ABSTRACT

The invention is related to a method of the manufacture of an implantable lens from a liquid polymer precursor in an open mold, during which the liquid polymer precursor in metered into the open mold in a such measured amount, that comes into contact with a functional shaping inner surface of the open mold, which is located under a peripheral circular sharp edge of the stationary open mold or which reaches up to this peripheral circular sharp edge, at which point the open mold, which contains the liquid polymer precursor, is rotated around it&#39;s vertical axis at a speed, at which the edge of the surface of the liquid polymer precursor reaches the peripheral circular sharp edge of the open mold, after which the liquid polymer precursor is exposed to conditions, under which it transforms itself into a state of a clear solid polymer by polymerization and/or cross-linking, until such time, at which the stated transition is attained, and then the implantable intraocular lens is removed from the open mold. The invention also includes the open mold used for the implementation of the stated method and the lens produced in this way.

FIELD OF THE INVENTION

The invention addresses a method of manufacture of an implantableintraocular planar/convex, biconvex, planar/concave or convex/concavelens, an open mold used for the execution of this method, and a lensmade using this method.

BACKGROUND OF THE INVENTION

Intraocular lenses are lenses implantable into the eye for the purposeof the change of correction. They can be implanted into various parts ofthe eye, such as the posterior chamber, anterior chamber, or stroma.Intraocular lenses are made of material of various rigidity. In case ofhard materials, such as certain poly(alkylmethacrylate)s, especiallypolymethylmethacrylate, or dehydrated hydrogels, also called xerogels,the most common manufacturing process is lathe machining with subsequentpolishing. Soft intraocular lenses are usually made by casting inappropriate molds. Casting is based on filling the mold with a liquidpolymer precursor, such as for instance a mixture of specific monomers,a melted polymer, or a liquid pre-polymer with a cross-linkingcapability, and on the subsequent conversion of this material into asolid state, known as solidification. In case of soft materials forintraocular lenses, this solidification generally includescross-linking, i.e. the formation of a three-dimensional covalentnetwork, which stabilizes the shape of the lens. For example, thisnetwork can be formed by either the copolymerization of bi-fuctionalmonomers with multi-functional cross-linking co-monomers, known ascross-linking agents or cross-linkers, or the additional cross-linkingof the liquid polymer.

The transition from a liquid to a solid state is accompanied by agreater or lesser volumetric contraction, which greatly complicates thecasting of the product, for which a great shape accuracy is required,such as in case of intraocular lenses.

The casting process can be realized relatively easily using liquidprecursors, in whose case cross-linking results in a small volumetriccontraction. An example of such liquid precursors are silicon rubbers.

Most contemporary intraocular lenses is based on the cross-linking ofacrylic or methacrylic polymers, however, which are generally made usingcross-linking copolymerization of a mixture of acrylic and/ormethacrylic monomers. Such monomer mixture contains at least one type ofa monomer with one polymerizable double bond, representing basic monomeror monomers, and at least one type of a monomer with two or morecopolymerizable double bonds, representing the cross-linking co-monomeror co-monomers.

Basic monomers form the main polymer chain in course of polymerization,while the cross-lining co-monomers form covalent bridges between thechains. The result of this copolymerization is the formation of athree-dimensional network, which is non-meltable and insoluble in anysolvent. The process described above is often used in case of hydrogels.

If, for example, the basic monomer is 2-hydrozyethylmethacrylatecopolymerized with a small amount, usually no more than 2% molar, ofethylendimethacrylate functioning as a cross-linker, it will form across-linked poly(hydroxyethylmethacrylate). Such hydrogels aredescribed, for example, in the U.S. Pat. Nos. 2,976,576 and 3,220,960,and are the basis for many contact lenses and various implants,including intraocular lenses.

Ophthalmic lenses are made using various shaping processes, for examplepolymerization in closed molds. Closed molds are not particularlysuitable for cross-linking copolymerization, however, which is followedby a significant volumetric contraction amounting to up to 20% of thevolume. If the volume of the closed mold cavity is constant, then thecontraction results in the decrease of pressure within the molds, whichhas many undesirable consequences, particularly the formation ofcavities, bubbles, vacuoles, and surface defects. The contraction duringsolidification is a common problem in the shaping of plastics, which issolved in various ways, for instance gradual addition of additionalliquid precursor, by which the loss of pressure due to contraction iscompensated, such as during injection molding of thermoplastic resins.

This technique is practically unusable in case of cross-linkingcopolymerization, however, because the gel point, which is a state atwhich the three-dimensional network is created and the flow capabilityof the copolymerized product is halted, is here reached at very lowdegrees of conversion. A significant contraction occurs at the pointwhere it is not possible to add further liquid precursor.

These difficulties during cross-linking copolymerization in closed moldsled to the search for alternative casting technologies. The casting ofoptical components, such as ophthalmic lenses, requires an extremelygood shape definition, excellent surface quality, and materialhomogeneity, in other words qualities unattainable if the overpressurein the cavity of the closed mold is not maintained. The patentliterature shows many proposed solutions to this problem. One of theseis the casting while the mold is rotating, which is known under it'soriginal name “spin-casting”, and which was, for example, proposed forthe production of hydrogel contact lenses in the U.S. Pat. Nos.3,660,545, 4,517,138, 4,517,139, 4,517,140 and 4,551,086. This techniqueis used for the manufacture of contact lenses using an open concavemold, provided with a sharp edge forming the boundary of the form. Themold is filled with a small volume of a monomer mixture, which issignificantly smaller than the volume of the concave cavity of the mold.The level of Liquid monomer mixture is, in this case, always deep underthe plane of the sharp mold edge. Due to the mold rotation around thevertical axis of symmetry of the mold cavity, the liquid monomer mixturewill spread to form a concave shape, approaching a paraboloid. Theresult is a convex/concave lens, whose central thickness is very low,which means that it is significantly lower than the sagital depth of themold cavity. This shape is especially appropriate for hydrogel contactlenses. The speed of mold rotation for the manufacture of contact lensestypically lies between 300 and 500 rpm, with the mold cavity diameter inthe plane of it's sharp edge typically being between 13 and 17 mm.

Another known use of rotational casting is the formation of parabolicmirrors for telescopes and other instruments requiring precise focusing.In these cases, the goal is the creation of parabolic optical surfaceswith a single focus for coaxial rays and without spherical aberration.

The U.S. Pat. No. 3,691,263 describes a different method of rotationalcasting, where the casting of contact lenses is done without the use ofmolds. It involves the polymerization of liquid monomers on the surfaceof a rotating carrier liquid, which is non-miscible with polymerizingliquid monomers, which has a higher density than polymerizable liquidmonomers, and which is for example mercury or a concentrated salinesolution.

Another modification of this process uses monomer polymerization on theinterface of two rotating non-miscible liquids, of which one has higherand the other one has a lower density than the starting monomer and theresulting polymer.

The U.S. Pat. No. 4,806,287 describes a method of lens manufacture usinghydrophilic gels. This method is based upon the solidification of adroplet of a monomer under a non-miscible liquid, such as oil, while atleast the optical zone of the lens is formed between a mold and anappropriately shaped plunger. One option mentioned is also moldrotation, where the mold rotation does not affect the optical zone ofthe lens, which is defined by the shape of the plunger, but it affectsonly the peripheral parts of the molding. For that reason, this lenscannot be considered a rotationally-cast lens.

Rotational casting on liquid surfaces of a high specific gravity can bealso used for the casting of precise tubing made of cross-linkedpolymers, as described by the Czech patent CZ 153760.

So far, rotational casting has not been utilized for the production ofintraocular lenses for several reasons. First of all, most intraocularlenses made until now has a relatively small diameter, which is usuallyequal to no more than 6 mm. It was assumed that centrifugal castingwould have only a limited effect on the shape of the lens for suchdiameters, because the centrifugal force increases with the square ofthe distance from the rotation axis. Beside that, intraocular lenses aregenerally biconvex, or less frequently planar-convex lenses, androtational casting has been up to date used only for lenses which aredistinctly convex/concave lenses, such as in the case of contact lenses.Finally, contemporarily manufactured intraocular lenses often havecomplex shapes of a non-circular footprint, with the optical zone andintegral haptics for centering the lens in the eye. Such shapes withnon-circular shape are not suitable to rotational casting in open molds.Due to the reasons listed above, rotational casting of intraocularlenses has been until now considered unfeasible by the experts in thefield.

Until now, intraocular lenses have been made using casting into openstationary molds, where the meniscus formed by the liquid monomerdefined the shape of one of the optical surfaces. These methods aredescribed in the U.S. Pat. Nos. 4,971,732, 4,846,832, and 5,674,283.According to the U.S. Pat. No. 4,971,732 the liquid monomer mixture ismetered into a concave cavity provided with a sharp edge forming theboundary of the cavity. The material from which the mold is made ispoorly wettable by the monomer mixture. The volume of the liquid monomermixture dosed into the mold must be equal or preferentially higher thanthe volume of the mold cavity, so that the level of the liquid monomermixture will reach up to the sharp edge of the mold. If the amount ofthe liquid monomer mixture is insufficient is insufficient in thisrespect, the liquid filling the mold cavity will retract away from thesharp edge due to polymerization contraction; therefore it is impossibleto obtain a quality product in this case. Therefore it is beneficial toincrease the metered volume of the liquid monomer mixture and thusattain a higher meniscus. The volumetric excess of the monomer inrespect to the mold cavity volume and thus also the height of themeniscus affect the optical power of the lens. For this reason, it ispossible to create lenses of various optical power using one mold, bymetering various volumes of liquid monomer mixture into the cavity.

A typical product of this process is a biconvex intraocular lens with adiameter over 9 mm, central thickness 2.5 to 6.3 mm, frontal opticalsurface in the shape of a flat ellipsoid with a center radius from 7.5to 15 mm, rotationally symmetrical rear optical surface with a centerradius from 5 to 8 mm and toric transitional zone between both opticalsurfaces.

This typical product has several disadvantages. First, the centralthickness and the overall lens volume are too high for a small-incisionimplantation, which is required by today's surgeons. Secondly, the frontoptical surface in the shape of a flat ellipsoid is not advantageous,because it has a high spherical aberration. Furthermore, this surface isoften unevenly deformed by the polymerization in various parts of themonomer mixture proceeded at various rates, therefore the contractionwas not entirely uniform. This is a general disadvantage of staticpolymerization casting in open molds.

The U.S. Pat. No. 4,846,832 describes a soft biconvex intraocular lenswith a rear convex surface formed by the solidification of liquidmeniscus, while the front surface has a central convex zone with adiameter of 4 to 8 mm. The central zone is surrounded by the concavesurface of a relatively thin peripheral zone. The front side of the lensis therefore created by the imprint of the mold with a concave opticalcenter zone and a sharp circular rim at the edge. Since the rear side isformed by a solidified meniscus of the liquid, it probably also has theshape of a flat ellipsoid and therefore also has a high sphericalaberration. Intraocular lenses can be manufactured using this methodeither using silicone rubber, or a cross-linked hydrogel with arelatively high index of refraction at 1.42 to 1.43.

The U.S. Pat. No. 5,674,283 describes an intraocular lens in the shapeof a saucer with a biconvex optical zone, similar to the product of thepreceding method, but made using a different method. The main differenceis that in case of a lens made according to the U.S. Pat. No. 5,674,283the rear side of the lens is shaped by the cavity of the mold, while thefront side of the lens is shaped by the meniscus of the monomer, i.e.like in case of a lens made using the method in U.S. Pat. No. 4,971,732,and conversely of the lens made according to the method described in theU.S. Pat. No. 4,846,832. This method is a modification of the methodaccording to the U.S. Pat. No. 4,846,832 with the difference that theoptical surface creation by the use of the meniscus is used only in thecentral area of the lens. This method uses a two part form, where thetop part of the mold has a central circular window, in which themeniscus of the liquid monomer is formed. The diameter of the opticalzone is substantially smaller than the diameter of the whole lens.

The goal of the invention is to improve the production of intraocularlenses, which has been until now done using stationary casting in openmolds, described in the U.S. Pat. Nos. 4,971,732, 4,846,832 and5,674,283, and thus obtain a wider selection of attainable shapes andoptical power values, improvement of optical quality, and increase ofproduction yield of intraocular lenses. In the framework of theinvention, the technical prejudice according to which centrifugalcasting was deemed unusable for the production of intraocular lenses bythe technical community, has been overcome, and with a surprise thereverse has been found, that under the conditions defined by theinvention it was possible to produce intraocular lenses of requiredquality using centrifugal casting. Even though the centrifugal casting,used within the framework of the invention, was originally developed forcontact lenses, the conditions for the production of intraocular lensesaccording to the invention and the hitherto used conditions for theproduction of contact lenses are entirely different and not deduciblefrom one another, because the conditions, which are suitable forintraocular lenses, are not usable for contact lenses, and vice versa.The method according to the invention differs from the current state oftechnology even by technical problems, which it solves. While in case ofimplantable intraocular lenses the invention solves problems ofstationary casting in open molds and the removal of some of its'shortcoming, the spin casting of contact lenses did not originate instationary casting in open molds, because contact lenses cannot be madeby stationary casting in open molds at all, and casting while rotatingin case of contact lenses thus did not attempt to solve technicalproblems of stationary casting, but it solved entirely different set oftechnical problems, which are problems associated with contraction inclosed molds. In the scope of this invention it was discovered, thatimplantable intraocular lenses can be advantageously manufactured byrotational casting under conditions specified below, while the result ofthe method according to the invention is, furthermore, an implantableintraocular lens with a unique configuration and useful characteristics.

SUMMARY OF THE INVENTION

The subject of the invention is a method of manufacture of animplantable intraocular planar/convex, biconvex, planar/concave orconvex/concave lens made from a liquid precursor of the polymer, whichis able of being transformed into a clear, solid polymer throughpolymerization and/or cross-linking in an open mold, the said moldhaving a functional shaping inner surface that is separated from theremaining surface of the open mold by a peripheral circular sharp edge,the functional shaping inner surface being unwettable or incompletelywettable by the liquid precursor, wherein the said method comprises thefollowing steps:

a) the liquid polymer precursor is metered into the open mold in theamount, at which the edge of the surface of the liquid precursorcontacting the inner surface of the open mold is located under theperipheral circular sharp edge of the open mold or reaches thisperipheral circular sharp edge and at least a part of the surface of theliquid polymer precursor will protrude above the plane defined by theperipheral circular sharp edge of the open mold, or at least a part ofthe surface of the liquid precursor lies in this plane or the wholesurface of the liquid polymer precursor lies below his plane, while inthis case the liquid polymer precursor will be metered into the openmold in the amount, which will always be higher than the amount of theliquid polymer precursor needed to obtain a contact eye lens of the samediameter.b) the open mold, which contains the liquid polymer precursor, isrotated around its vertical axis at a speed, at which the edge of thesurface of the liquid polymer precursor reaches to the peripheralcircular sharp edge of the open mold, the liquid polymer precursor is incontact with the whole inner surface of the open mold and the surface ofthe liquid polymer precursor is located in the plane defined by theperipheral circular sharp edge, or finds itself above or below thisplane,c) the liquid polymer precursor is exposed to conditions, under which itwill be able of its transformation into a state of a clear, solidpolymer by polymerization and/or cross-linking;d) and the open mold continues to be rotated at the said speed at leastuntil the time, when the edge of the surface of the polymerized and/orcross-linked liquid polymer precursor reaches the peripheral circularsharp edge of the open mold even if the rotation of the mold during wasslowed down or stopped;e) then the rotation of the open mold is optionally slowed down orstoppedf) and the exposure of the contents of the open form to the conditions,during which its transition into clear, solid polymer state throughpolymerization and/or cross-linking continues at least until such time,when the said transition is attained,g) whereupon the implantable intraocular lens is removed from the openmold.

Preferably, the liquid polymer precursor contains at least one monomerwith at least one double bond polymerizable by a free radicalpolymerization.

Preferably, the radical polymerization is initiated by the fission ofinitiators containing a peroxide bond or azo-bond.

Preferably, the radical polymerization will be initiated using freeradicals created by the action of radioactive or electromagneticradiation or the action of accelerated electrons.

Preferably, the monomers with at least one double bond which ispolymerizable by radical polymerization are derivates of acrylic and/ormethacrylic acid.

Preferably, at least one of the derivates of acrylic and/or methacrylicacid is an ester of a polyhydric compound with at least two molecules ofacrylic or methacrylic acid.

Preferably, at least one of the derivates of acrylic and/or methacrylicacid is a salt of the acrylic or methacrylic acid.

Preferably, at least one of the monomers with at least one double bondpolymerizable by radical polymerization contains a group capable ofabsorbing electromagnetic radiation in the range between 190 and 500 nm,advantageously between 300 and 400 nm.

Preferably, the group capable of absorbing electromagnetic radiation isderived from benzophenone or bentriazole.

Another subject of our invention is an open form for the implementationof the method defined above, whose concept is based upon it's containingan open concave cavity, defined by a functional shaping concave innersurface ending by a peripheral sharp edge having the shape of a circle,which lies in the plane perpendicular to the vertical axis of the openconcave cavity and has a diameter of 5 to 10 mm.

Preferably, the radius of the curvature of the open concave cavityincreases from the lowest value in the proximity of the vertical axis ofthe open concave cavity in the direction toward the peripheral circularsharp edge of the open concave cavity.

Preferably the functional shaping concave inner surface of the openconcave cavity has the shape defined by the rotation of a section of acone along the vertical axis of the open concave cavity.

The section of the cone is preferably defined by the equationY=−a+(a/b)·(b²+X²)^(0.5), in which a=R_(c)·(1+h), while R_(c) is thecenter curvature radius and h is the parameter defining the asphericity,which is chosen from the interval from −1 to +infinity.

The parameter defining asphericity h is preferably chosen in theinterval from −0.75 to +1.

The center curvature radius R_(c) is chosen from a value in the intervalfrom 2 to 20 mm, preferentially in the interval from 2.5 to 5 mm.

The peripheral sharp edge has preferably the shape of a circle, with adiameter from 7 to 9 mm. The open concave surface cavity preferablypasses in the upper part of the open mold over an intermediate circularedge having the shape of a circle lying in the plane that is parallel tothe plane of the peripheral sharp circular edge, into a transitionalopen cylindrical or frustum-of-a-cone cavity limited between theperipheral sharp edge and the intermediate circular edge.

Preferred height of the transitional open cylindrical orfrustum-of-a-cone cavity is from 0.01 to 0.2 mm, and even morepreferably from 0.03 to 0.08 mm.

The preferred volume of the open concave cavity, or optionally thecombined volume of the open concave cavity and the transitional opencylindrical or frustum-of-a-cone cavity is from 15 to 175 μm, even morepreferably from 25 to 55 μm.

According to the invention, the mold is preferably made of a plasticmaterial which is not wettable or is incompletely wettable by the liquidpolymer precursor.

Preferably, the mold according to the invention is made from apolyolefin.

The subject of the invention is also an implantable intraocularplanar/convex, biconvex, planar/convex or convex/concave lens producibleby the above defined method according to the invention, or producible inthe above defined open mold according to the invention.

DESCRIPTION OF FIGURES ON DRAWINGS

The attached drawing in FIG. 1 shows a preferred cross-section of themold according to the invention, whose cavity is formed by a combinationof an open concave cavity and a transitional open cylindrical cavity;

FIG. 2 shows a partial cross-section of another preferred open moldaccording to the invention, whose cavity is formed by the combination ofan open concave cavity and a transitional open frustum-of-a-cone cavity;

FIGS. 3A to 3C show a schematic of rotational casting in an open moldaccording to the invention at various levels of filling of the open moldby a liquid polymer precursor;

FIG. 4 shows a schematic representation of rotational casting in an openmold according to the invention at various rotational speeds of the openmold;

FIG. 5 shows a preferential specific open mold according to theinvention.

According to the invention, intraocular lenses can be made according tothe invention from various cross-linked polymers. Within the scope ofthe invention, advantageous polymers are such, whose temperature ofsoftening while in an equilibrium state with intraocular fluids is lowerthan the body temperature. Such polymers can be based on silicones, forexample such as are described in U.S. Pat. No. 5,519,070. Further, thosepolymers can be hydrophobic and hydrophilic acrylic or methacrylicpolymers, polyurethanes or polyureas, which are described in U.S. Pat.No. 6,165,408. Especially advantageous are hydrogels suitable forophthalmic uses, which are, for instance, described in U.S. Pat. Nos.2,976,576, 3,220,960, 5,224,957, 4,775,731, 4,994,083, 4,997,441,5,002,570, 5,158,832, 5,270,415, 5,910,519, 5,698,636, 5,391,669,5,674,283, 5,158,832 and 6,372,815. Of these, especially appropriate arethe covalently cross-linked copolymers containing acrylic and/ormethalcrylic acid and their derivatives, such as esters, amides, orsalts. The most suitable are cross-linked copolymers of hydrophilicmethacrylates.

At least a part of a copolymer is formed by a copolymerizable monomerable to absorb radiation of a wavelengths between 290 and 500nanometers, preferentially between 300 and 400 nanometers. Suchmonomers, based for example on the derivates of benzophenone orbenz-triazole are well known to experts in the field. An example arecopolymers absorbing ultraviolet radiation described in U.S. Pat. No.5,133,745.

Solidification of the liquid precursor can be accomplished by thepolymerization of a mixture of basic and cross-linking monomers.Suitably, such polymerization is a radical polymerization and isinitiated by either the usual free-radial initiators or by aphotoinitiation mechanism. Radical polymerization can be initiated byelectromagnetic radiation in various areas of the spectrum, for examplein the visible radiation area, ultraviolet radiation, x-rays, or gammaradiation. Free radicals can potentially be created even by absorbanceof free electrons from beta-radiation or electrons accelerated using anelectrical field. Solidification can also be performed by cross-linkingby liquid polymer precursors, for instance such as reactive siliconepre-polymers or polyvinylalcohol solutions. Photo-initiatedpolymerization or cross-linking are especially advantageous methods, andare described, for example, in U.S. Pat. Nos. 6,190,603 and 5,224,597.It is desirable that the metering of the liquid precursor is performedwith the accuracy better than 1 mg, and preferably with accuracy betterthan 0.1 mg. The rotation of the open mold, containing the liquidpolymer precursor, can be implemented using various techniques and whileusing various equipment, which are described in U.S. Pat. Nos.3,660,545, 4,517,138, 4,517,139, 4,517,140 and 4,551,086. If certaincomponents of the precursor polymer mixture are relatively volatile, itis possible to limit evaporation by keeping the mold with the liquidprecursor in an enclosed system with a very small space for the gasphase while undergoing solidification. Such methods and equipmentsuitable for rotary casting of lenses made from volatile monomers aredescribed in U.S. Pat. No. 4,680,149.

An advantageous design of an open mold for the execution of the methodsaccording to the invention is depicted in FIG. 1. Open mold 1 contains,first, the open concave cavity 2, which is defined by the functionalshaping concave inner surface 3 and the intermediate circular edge 4,and second, by the transitional open cylindrical cavity 5, defined bythe functional shaping cylindrical inner surface 6, intermediatecircular edge 4 and the peripheral circular sharp edge 7. Both theinserted circular edge 4 and the peripheral circular sharp edge 7 lie inplanes, which are perpendicular to the vertical axis 8 of the cavity ofthe open form 1. The distance of these mutually parallel planesdetermines the height Hv of the transitional open cylindrical cavity 5;the distance of the plane on which the peripheral circular sharp edge 7lies, from the cross-section of the vertical axis 8 of the cavity of theopen mold 1 with the functional shaping concave inner surface 3determines the sagital depth S of the cavity of the open mold 1; and thediameter of the circle, which is created by the peripheral circularsharp edge 7, determines the peripheral diameter D of the cavity of theopen mold 1. The body of the open mold can be made of various materials,however the most advantageous material is a plastic. Of plastics, themost advantageous are polyolefins, such as polyethylene orpolypropylene. The material, from which the open mold is made, is chosenso that is not easily wettable by the liquid polymer precursor. Thewetting angle is preferentially higher than 30°, and even better, higherthan 90°. The open mold can be, preferentially, designed for single useand made by injection molding.

The functional shaping surface of the cavity of the open mold does notnecessarily have to be symmetrical. It can, in principle, have any shapedesired as long as the inserted circular edge 4 and the peripheralcircular sharp edge 7 are indeed circular. The open mold cavity can becreated by a combination of a spherical and a cylindrical plane, forexample, such as necessary for the compensation of astigmatism. However,the most usual are rotationally symmetrical surfaces with the axis ofsymmetry identical with the vertical axis 8 of the open mold cavity. Themost advantageous are planes created by the rotation of a part of aconical section, including a circle, ellipse, parabola, hyperbola, ortheir various combinations. Various parts of the functional shapingsurfaces of the open mold cavity can be formed by the rotation ofvarious curves. Thus can be, for example, the central part of the innershaping surface of the open mold cavity formed by a spherical surface,while the remainder of the inner shaping surface toward the edge of theopen mold cavity can be formed by truncated cone surface. Anotherexample are surfaces composed from concentric segments with variouscurvatures, enabling the creation of a bifocal or a polyfocalintraocular lens.

In the scope of the invention, the most advantageous are smooth surfacescreated by the rotation of one continuous curve, which has the lowestradius of curvature in the proximity of the vertical axis 8 of the openmold cavity and whose radius of curvature gradually increases with theincreasing distance from the abovementioned vertical axis 8. Such anadvantageous surface can be created by the rotation of a hyperbola,which can be approximated in the following equation using the orthogonalcoordinates X and Y:

Y=−a+(a/b)·(b ² +X ²)^(0.5)

where

a=R _(c)·(1+h)²

b=R _(c)·(1+h)

while R_(c) is the center curvature radius and h is a parameter definingthe asphericity of the surface. Parameter h can be chosen in theinterval from −1 to +infinity. The curve described by the equation (1)approaches a straight line, when h approaches −1, and it approaches acircle, when H approaches +infinity. Within the scope of the invention,the most advantageous values of h are between 40.75 and +1, when theresulting surface is significantly aspherical and its optical powerdecreases from its maximum central value toward its minimum peripheralvalue. Intraocular lens created under these conditions is thenpolyfocal. Apshericity and polyfocality are enhanced with a loweringvalue of the parameter h. Molds for rotational casting of contact lensesusually have a cavity in the shape of a spherical cap and the value ofthe parameter h in their case approaches infinity. This proves, thatknown molds for contact lenses and molds for implantable lensesaccording to the invention are not mutually interchangeable even fromthis point of view.

The value of the center radius of curvature R_(c) is chosen in theinterval from 2 to 20 mm, advantageously from 2.5 to 5 mm. Once again itis necessary to emphasize, that the mold with a cavity of such shapewould be entirely unusable for the casting of contact lenses, whileconversely, the shapes of open mold cavities used for contact lenses arenot usable for the production of intraocular lenses according to theinvention.

The shape of the edge of the open mold's cavity according to theinvention is important both for the production process and for thefunction of the resulting implantable intraocular lens. The advantageousshape of the edge of the cavity of the open form 1, according to theinvention, is depicted in FIG. 2, which depicts a partial section of theedge of the open mold. It is apparent in FIG. 2 that the cavity of theopen mold 1 is in this case created, first, by the open concave cavity2, defined by the functional shaping concave internal surface 3 and it'sintermediate circular edge 4 and second, by the transitional openfrustum-of-a-cone cavity 9, that is defined by the intermediate circularedge 4 by the peripheral circular sharp edge 7, and the functionalshaping frustum-of-a-cone inner wall 10. The slopes of the functionalshaping concave surface 3 and the functional shaping frustum-of-a-coneinner wall 10 are defined in FIG. 2 by angles α₁ and α₂, while angle α₁ranges advantageously from 75° to 175°, even more advantageously from−90° to 105°, while angle α₂ ranges advantageously from 60° to 135°, andeven more advantageously from 75° to 105°. The peripheral diameter ofthe cavity D ranges from 5 to 10 mm, advantageously from 7 to 9 mm. Thesagital depth of cavity S ranges advantageously from 0.75 to 5 mm, evenmore advantageously from 1 to 2.3 mm.

It is necessary to emphasize again, that open molds of these dimensionsare entirely unsuitable for rotational casting of contact lenses,because the peripheral diameter of molds used for contact lensproduction generally ranges from 13 to 17 mm. The volume of cavity V_(c)of the open mold can be calculated as the volume of the space defined bythe functional shaping inner surface of the open mold cavity and theplane of the peripheral circular sharp edge of the open mold. Thisvolume of cavity V_(c) advantageously ranges, in case of an open moldaccording to the invention, between 15 and 175 μl, even moreadvantageously between 25 and 55 μl. Open molds for contact lensproduction have much higher volumes of the cavity V_(c), generallybetween 200 and 600 μl.

The metered volume V₁ of the liquid polymer precursor can be changed ina broad range in dependence on the geometry of the mold, but as a ruleit ranges from approx. 10 to approx. 100 μl. If V₁<V_(c), then theliquid polymer precursor does not reach the peripheral circular sharpedge in a stationary mold. Rotation of the open mold is in his casenecessary to wet the whole functional shaping inner surface of the openmold cavity. However, the contraction of polymer precursor duringsolidification, which generally accounts for approximately 20% of thevolume, would cause the liquid in the open mold retract from theperipheral circular sharp edge. Therefore, this would result inrendering the shape of the intraocular lens worthless. This undesirablephenomenon can be prevented by rotating the open mold at a sufficientlyhigh rate of rotational speed. Contraction during solidification can becharacterized by a contraction factor C, which is the ratio of thespecific gravities of the polymer precursor before and aftersolidification (d_(m) and D_(p)): C=d_(m)/d_(p).

The value of the contraction factor C can change across a wide rangefrom about 0.8 to a value close to 1. Overall it is desirable, that thedosed volume V₁ of the liquid polymer precursor was in a particularratio to the volume of cavity V_(c). This filling ratio Z=V₁/V_(c)ranges from about 0.75 to about 2, advantageously from about 0.95 toabout 1.5. As a matter of comparison, the filling ration used in case ofcontact lenses is Z<<0.5, typically in the interval of values from 0.05to 0.2. It can be then stated, therefore, that the values of the fillingratio are much higher for implantable lenses according to the invention,than values useful for contact lens production using rotational casting,whereas conversely, the values of the filling ratio usual for contactlenses are not usable for the method of intraocular lens productionaccording to the invention.

The surface quality of polymers created in open stationary molds isoften bad due to uneven course of polymerization, which leads to unevencontraction and thus to surface deformation. This is a problemespecially in case of cross-linking polymerization, where thepolymerization rate increases significantly with viscosity, that is withthe rate of reaction conversion. This increase of reaction rate inespecially sharp at gel-point, where a three-dimensional continuousnetwork is just created, which is known as the so-called TrommsforfEffect. This undesirable phenomenon is significantly limited by therotation of the mold, even at very low rotation speeds. On one hand thespeed of initiation is equalized throughout different parts of thecavity, on the other hand, the rotation helps to stabilize the shape ofthe liquid surface. Both influences cause the quality of the product'ssurface to be greatly improved as a result of rotational rather thanstationary casting. Centrifugal force developed by the mold's rotationspreads the liquid polymer precursor in the direction away from thevertical axis of the open mold cavity and toward the edge of the openmold, until the edge of the level of liquid polymer precursor reachesthe perimeter circular sharp edge of the open mold and remains incontact with the peripheral circular sharp edge until the solidificationof the polymer precursor, i.e. until such viscosity of the form's fillis reached at which the precursor practically does not flow and remainsin contact with the peripheral circular sharp edge even in the case thatthe rotation of the mold ceases. In case of cross-linkingpolymerization, this state already occurs at lower degrees ofconversion, for instance at a degree of conversion of 3-5%.

This is represented schematically in FIGS. 3A to 3C, in which the openmold according to the invention was already described in detail inreference to FIG. 1. The cavity of this open mold is created by acombination of an open concave cavity and a transitional opencylindrical cavity.

FIG. 3A demonstrates a situation where the filling ratio is Z<1, wherethe volume of cavity V_(c) of the open mold is higher than the meteredvolume V₁ of the liquid polymer precursor. The liquid polymer precursoroccupies the stationary surface S in an open resting mold, and arotational surface R while the mold is being rotated at a speed, atwhich the level of liquid precursor reaches the peripheral circularsharp edge. As evident from FIG. 3A, the original convex meniscus of theliquid will change to a concave. As long as Z=V₁/V_(c)<1, the rotationalspeed of the open mold must be relatively high and the front surface ofthe manufactured intraocular lens will be concave with a negativerefractive power. With the increasing rotational speed of the open mold,with the increasing peripheral diameter D of the open mold's cavity,with the lowering contraction factor C and with the lowering fillingratio Z=V₁/V_(c), the concavity of the front wall of the intraocularlens will increase, and with it the overall positive optical power ofthe lens will decrease.

FIG. 3B demonstrates a situation with a filling ratio Z=1, therefore theone where the metered volume V₁ of the liquid polymer precursor isexactly equal to the volume of the cavity V_(c) of the open mold. Inthis case a stationary planar surface S will be formed in the stationaryopen mold. During mild rotation around the vertical axis of the openmold, the rotational surface R has a slightly concave meniscus in thecenter of the surface, and at the edges the surface slightly exceeds theperipheral circular sharp edge of the open mold. In this case,rotational surface R has inflexion points. The speed of rotation of theopen mold is chosen such that the contact of the liquid polymerprecursor and the peripheral circular sharp edge is guaranteed but thatthe liquid polymer precursor does not spill over the peripheral circularsharp edge in the process. The chosen rotational speed of the open moldwill depend on a number of parameters, among which are especially thevolume V_(c) of the cavity, dosed volume V₁ of the liquid polymerprecursor, specific gravity of the liquid precursor before and aftersolidification, surface tension of the liquid precursor, and the wettingangle between the liquid polymer precursor and the functional shapinginner wall of the open mold's cavity. In course of the polymerization,the concavity of the level will become more pronounced due to thecontraction and a slightly convex/concave implantable lens will thus becreated.

In a case where the filling ratio Z=V₁/V_(c)>1 and Z·C=1, then at lowrotational speeds of the open mold an intraocular planar/convex lens canbe obtained, with an approximately zero optical power of the front side.The increase in rotational speed of the open mold will result in aconcave front wall of the intraocular lens with a negative contributionto the overall optical power. These conditions are specific forintraocular lenses, because they cannot occur during contact lensproduction.

With the increasing rotational speed of the open mold, with increasingperipheral diameter D of the cavity, with decreasing contraction factorC and with a lowering filling factor Z=V₁/V_(c), the front side of theintraocular lens will decrease in convexity and possibly increase inconcavity, which will also lower it's positive optical power.

FIG. 3C demonstrates a situation, during which the filling ratio is Z>1,and therefore where the dosed volume V₁ of liquid polymer precursor ishigher than the volume V_(c) of the open mold cavity. If the surface ofthe mold is not wettable or is at least poorly wettable by the liquidpolymer precursor, then even in this case the liquid polymer precursorwill not overflow over the peripheral circular sharp edge of the openmold. A convex meniscus will formed and the liquid polymer precursorwill reach a stationary surface S. As long as the condition Z·C>1 ismaintained, a biconvex intraocular lens will be formed through eitherpolymerization or cross-linking. During the rotation of the open moldalong the vertical axis, the level of liquid polymer precursor willchange its profile, and will reach a rotational surface R, whilst athigher rotational speed of the open form a planar or even a mildlyconcave central area will be created. In this case the level of liquidpolymer precursor at low rotational speeds of open mold, just as at azero rotational speed of the open mold, is essentially formed by a flatellipsoid, which has, as was already stated, a high sphericalaberration. Increasing the rotational speed of the open mold will resultin the lowering of the convexity of the central area of the intraocularlens, possibly even attaining a planarity or concavity of the centralarea of the intraocular lens. This leads to the decrease of thespherical aberration of the lens in this critical central region.

This is schematically depicted in FIG. 4, on which there is a picture ofan open mold, which was essentially already described in reference toFIG. 2, and whose cavity is created by a combination of an open concavecavity and a transitional open frustum-of-a-cone cavity. The surface ofthe liquid polymer precursor will assume rotational surface R1 at lowrotational speeds of the open mold, at medium speeds of the rotation ofthe open mold a rotational surface R2 and at high rotational speeds ofthe mold rotational surface R3. The highest usable rotational speed ofthe open mold is limited by the centrifugal force value at the edge ofthe cavity of the open mold, which may not exceed the cohesive force ofthe liquid polymer precursor resulting from it's surface tension. Ifthis highest usable rotational speed of the open mold is exceeded, itwill cause the liquid polymer precursor to spill over the peripheralcircular sharp edge and the contents of the mold will be renderedworthless. The rotational speed of the open mold, at which the overflowof the liquid polymer precursor occurs, is a critical parameter, whosevalue is specific for each given individual open mold and for each givenspecific polymer precursor.

Rotation during casting in open molds affords many advantages. Most ofall, it improves the filling of the open mold with the liquid polymerprecursor in the region of the intermediate circular concave edge.Because the material, from which the mold is made, is not easilywettable by liquid polymer precursor and this poor wettability isdesirable for the maintenance of a positive meniscus by the peripheralcircular sharp edge, the area of the open mold in the region of theinserted circular edge has a tendency to trap air bubbles duringstationary casting, which prevents the creation of a continuous sharpintermediate convex edge of the manufactured intraocular lens. Thisintermediate convex edge, which is formed by the intermediate circularedge of the cavity of the open mold, is important to the function of theinterocular lens, because it prevents the migration of cells along thelens and limits the occurrence of the phenomenon, known by the acronymPCO (Posterior Capsule Opacification; clouding of the posterior capsuleafter implantation) and which will be explained in further detail below.The rotation of the open mold generates a centrifugal force, which actsagainst the functional inner surface of the cavity and which thus helpsto force air out using the liquid precursor in this area. For thisreason, it is possible to form a sharper intermediate edge of theintraocular lens by rotational casting than in case of lensesmanufactured by stationary casting. Molds for contact lenses do not havean inserted circular edge at all, because in case of a contact lens, thecorresponding sharp inserted edge of the lens would be highlyundesirable.

Besides, the rotation of the open mold improves the quality of theperipheral edge of the intraocular lens, which is formed by theperipheral circular sharp edge of the open mold cavity, and which isdesirable for the biocompatibility of the intraocular lens. Liquidpolymer precursors often have a tendency not to entirely reach theperipheral circular sharp edge of the open mold, which occurs especiallyduring lower values of the filling ratio Z and at low wettability of thematerial, from which the open mold is manufactured. This leads to theformation of an irregular, jagged peripheral edge of the intraocularlens, which is not permissible for the desired function of theintraocular lens. The centrifugal force caused by the mold rotation,acting against the functional shaping inner surface of the open moldcavity, will push the whole edge of the liquid polymer precursor surfaceto the peripheral circular sharp edge position of the open mold, even atlow rotation speeds of the open mold, which contributes in a decisivemanner to the attainment of the required quality of the peripheral edgeof the intraocular lens.

Rotation of the open mold also positively affects the shape of themeniscus, because it shifts a portion of the liquid polymer precursorfrom the central area into peripheral areas and thus it flattens thecentral optical zone of the front side of the intraocular lens. Throughthis, a lessening of the spherical aberration of the front side of theintraocular lens will be attained, especially in the critical centraloptical zone.

Rotation of the open mold changes the central curvature of the frontside of the intraocular lens, and thus it also changes it's opticalpower. On account of this, one type of an open mold can be used for themanufacture of intraocular lenses of various optical powers, and thislowers the manufacturing cost.

The rotation of the open mold also improves the optical quality of thefront side of the lens, because it creates more uniform conditions forinitiation, especially in the case of photoinitiation, and it thusprevents uneven contraction of the content of the open mold that wouldotherwise lead to surface irregularities of the manufactured intraocularlens.

The speeds of rotation of the open mold can vary in various phases ofthe casting process. For instance, the rotation can be slower in thebeginning and the rotation axis does not need to be vertical, which willachieve a more uniform wetting of the functional shaping inner surfaceof the open mold cavity by the liquid polymer precursor, and this willsupport its' uniform spreading along the functional shaping inner wallof the open mold cavity. The rotation can then be speeded up in order toachieve a desired shape of the meniscus, or it can be slowed down andpossibly even stopped, in case where the whole edge of the level of theliquid polymer precursor reached the peripheral circular sharp edge ofthe open mold and that this position of the edge of the level of theliquid polymer precursor is already stabilized by the increasedviscosity of the liquid polymer precursor as a result of its'polymerization and/or cross-linking.

Rotational casting can be performed in various types of open molds andusing modified equipment for the rotational casting of contact lenses,which are described, for instance, in the U.S. Pat. Nos. 4,517,138,4,517,139, 4,517,140, 5,300,262, 5,435,943, 5,395,558, 5,922,249 and5,674,283.

After the solidification of the liquid polymer precursor, themanufacturing of the intraocular lens is more or less complete. Asopposed to other manufacturing processes for intraocular lensmanufacture, the method according to the invention does not requiremechanical operations, such as machining, lathing, filing and polishingof the obtained intraocular lens. According to the invention, theintraocular lens can be essentially made in one manufacturing step andwithout contact with a human hand. This is a significant advantage ofthe method according to the invention, because through this its'biocompatibility improves and the possibility of damage to the surfaceor the contamination of the intraocular lens is lowered.

The material, from which the open mold is made, can be selected so ithas low adhesion to the resulting cross-linked polymer. In such a case,manufactured intraocular lenses can be removed out of the mold without aprevious hydration. This, however, poses a risk to the intraocular lens,especially to its' delicate edges, which can be easily damaged due tothe fragility of the dehydrated material. It is therefore advantageousto hydrate the manufactured intraocular lens directly in the open mold,in which the intraocular lens was made. The hydration will soften theintraocular lens and further, it will lower its' adhesion to thefunctional shaping inner wall of the open mold cavity, therefore theintraocular lens will separate from the mold by itself.

The intraocular lens can then be rid of residual monomers and otherimpurities using extraction, using common methods, which were developedfor various types of implantable materials. The intraocular lens canalso has its' surface chemically modified to further improve its'properties, such as especially biocompatibility and the adhesion totissues. One of the possibilities for such surface modification ispartial surface hydrolysis while using basic or acidic catalysts,described, for instance, in U.S. Pat. Nos. 3,895,169, 4,997,441,5,080,683, 5,158,832 and 5,939,208.

The intraocular lens is finally packaged and sterilized using anappropriate method, for example steam sterilization.

The method according to the invention can be used for the manufacture ofvarious types of implantable intraocular lenses, such as are intraocularlenses designed to be implanted into the posterior chamber of the eye,intraocular lenses designed for the implantation into the anteriorchamber of the eye or intraocular lenses designed to be implanted intothe stroma. Such intraocular lenses can be manufactured using varioustypes of cross-inked polymers. Especially advantageous implantable lens,which perfectly utilizes the advantages afforded by the method accordingto the invention and thus it simultaneously affords large advantages forpatients, is characterized by at least some of the followingcharacteristics.

-   -   The optical zone is of a large diameter, typically between 6 and        9 mm. Large optical zone is of a large advantage for vision,        especially at night, when the iris is dilated and the edge of a        small optical zone falls into the optical path in lenses made in        current state of technology, and causes reflections, blinding by        too much light, loss of contrast, or other undesirable effects.    -   Aspherical polyfocal optics with a maximum positive optical        power in the middle, gradually falling in the direction of the        edges. This type of optics compensates spherical aberration, has        high depth perception and can cause pseudo-accommodation,        especially the adjustment for long-distance vision under        poor-light conditions.    -   Smooth and continuous convex rear side of the intraocular lens        fits well into the rear capsule of the original lens. This helps        to keep the rear capsule naturally taut, and this lowers the        incidence of clouding of the rear capsule after implantation.    -   Whole surface of the intraocular lens, with the exception of the        peripheral edge and possibly the intermediate edge, is        continuous, i.e. without breaks and ridges. This improves both        the optical quality and the biocompatibility of the lens.    -   The sharp and uninterrupted intermediate ridge of the        intraocular lens, in contact with the posterior capsule, limits        cell migration into the space between the lens and the capsule,        and thus it lowers the incidence of the posterior capsule        opacification after implantation.    -   Axial deformability of the intraocular lens. Because of its'        shape, the intraocular lens can be deformed using front-back        pressure of inner-eye structures, comprising the cilliary body,        the zonules and the vitreous body, and thus allowing the change        the curvature of its surfaces and making it possible to simulate        the natural accommodation of the eye. Intraocular lenses of        other shapes, falling under the current state of technology, do        not have this capability and have to depend on their        displacement in the front-rear direction; therefore the        pseudo-accommodation ability are significantly worse in their        case.    -   A relatively high water content in the equilibrium state with        inner-eye fluids. Under these conditions, the water content is        higher than 30% of mass, and advantageously higher than 40% of        mass. High water content enables dehydration during deformation        and thus the creation of a refractive index gradient, which        further increases optical power and contributes to        pseudo-accommodation. High water content also lowers surface        reflectivity of the lens, increases its' biocompatibility, and        enables its' implantation through a smaller surgical opening,        and that in a partially or wholly dehydrated state.    -   The hydrogel of the poly(hydroxyethylmethacrylate) type        containing carboxyl groups, especially cross-linked copolymers        containing 2-hydroxyethylmethacrylate and methacrylic acid. The        content of carboxyl groups is advantageously between 0.25 and 7        mol. %, and especially advantageously between 0.3 and 3 mol. %.        Even though it is often stated that methacrylic acid is not        desirable in contact or intraocular lenses, because it binds        Ca²⁺ and causes calcification, in the scope of the invention it        was shown to be quite the opposite. It appears that the carboxyl        groups suppress calcification, which can be observed in certain        hydrogels, and overall they improve the biocompatibility of the        hydrogel. Carboxyl groups can be introduced into the hydrogel in        the course of its' preparation during the copolymerization of        the basic monomer with acrylic or methacrylic acid, or it can be        generated in an already finished hydrogel by using partial        hydrolysis of ester groups. Hydrolysis can be catalyzed by both        acids or bases.

In the following part of the description, the invention will be furtherelucidated using examples of it's specific execution. These examples areonly meant to illustrate, and they do not limit the scope of theinvention any way, because it is clearly delineated by the definition ofthe present claims and the contents of the present description.

EXAMPLES Example 1 Comparative

For the production of intraocular lens, an open mold was used, which isschematically depicted in a cross-section in FIG. 5, and which has thefollowing parameters:

diameter at edge D=7.75 mmsagital depth S=1.34 mmcenter curvature radius Rc=3.50 mmradius of curvature outside of the center Rnc=9.10height of the transitional open cylindrical cavity Hv=0.05 mmangle α1=35′,angle α2=90°,volume of cavity Vc−37.1 μl,and a monomer solution of the following composition by weight:2-hydroxymethacrylate 98.6%ethylglycoldimethacrylate 0.25%diethylenglycoldimetbacrylate 0.1%triethylenglycoldimethacrylate 0.1%methacrytic acid 0.4% anddiisopropylcarbonate 0.5%.

This basic monomer mixture is combined with glycerol using the ratio of9 weight units of monomer mixture to 1 weight unit of glycerol. Theobtained monomer mixture is purged with argon for a period of 2 minutes,after which the cavity of the open mold defined above is filled with 45μl of the above described monomer mixture. The open mold with themonomer mixture is then heated to a temperature of 70□ C. for a periodof 6 hours without the open mold being rotated. The obtained hardxerogel intraocular lens is inspected prior to its removal from the openmold. The central part of its meniscus is partially indented due to theinfluence of contraction, and somewhat wavy. The waviness is uneven andhas a form of either concentric circles, or accordion pleats. The edgeof the intraocular lens is somewhat uneven and partially deformed, withincorporated bubbles. The intraocular lens is allowed to swell in theopen mold using 1% solution of sodium bicarbonate, and then it isremoved from the open mold and extracted 10 times in an excess of a 0.9%solution of sodium chloride. The water content inside the intraocularlens after the last extraction amounts to 42% by weight, and in auniformly swollen intraocular lens, the dimensions are as follows:diameter 8.9 mm, center thickness 1.4 mm.

Optical strength of the intraocular lens was measured on the NIKON PL2instrument, during which process the intraocular lens was immersed in aisotonic salt solution and at aperture 3 mm. Even at the best attainablefocusing of the intraocular lens, the measuring cross-hairs were blurreddue to the deformation of the optical surface of the intraocular lens,and therefore the measurement could not have been done with sufficientaccuracy. The best estimate of the optical power is +15 diopters.

Example 2 According to the Invention

The process according to Example 1 is repeated, however glycerol is notadded to the basic monomer mixture and the open mold with the monomermixture is rotated for the first hour of polymerization at a speed of 30rpm, whereas the rotation of the mold is halted and the polymerizationcontinues under stationary conditions for a period of another 6 hours.Due to the polymerization, the meniscus of the monomer mixturesolidifies into a smooth, slightly concave surface after only one hour,and it will not change even after subsequent finishing polymerization,which is done without rotating the open mold. The edges of thus obtainedintraocular lens are sharp and clearly defined, without defects visibleat a 20× magnification. The intraocular lens has a hydrated-statediameter of 9.4 mm with a central thickness of 1.6 mm. The optical powerof the intraocular lens is readily measurable, and the focusing patternis clear and crisp. The refractive power is +14.75 diopters.

Example 3 According to the Invention

The monomer mixture from the Example 1 is modified, so that it'sglycerol content is increased to 20% of it's mass, and 35 μl of thismixture is dosed into the open mold cavity. The rotational speed of theopen mold is first set for 5 rpm at a room temperature and a tilt of therotational axis at 30° from the vertical, and then is speed ismaintained for a period of 5 minutes. Then the temperature is increasedto 70° C., the rotational axis is shifted to a vertical position and thespeed of rotation is increased to 360 rpm. The edge of the surface ofthe monomer mixture rises up to the peripheral circular sharp edge ofthe open mold, and the open mold is rotated under these conditions for 6hours under a protective nitrogen atmosphere. Other steps the processare the same as the corresponding steps stated in Example 1. Thusobtained hydrated intraocular lens has a convex/concave shape, adiameter of 8.5 mm, sagital depth of 1.2 mm and a diopter value of +12.5diopters.

1-22. (canceled)
 23. The method of manufacture of the implantableplanar/convex, biconvex, planar/concave or convex/concave lens made froma liquid polymer precursor, which is capable of a transition into aclear, solid polymer state by polymerization and/or cross-linking in anopen mold, the said mold having a functional shaping inner surface thatis separated from the remaining surface of the open mold by a peripheralcircular sharp edge, the functional shaping inner surface beingunwettable or incompletely wettable by the liquid precursor, wherein a)the liquid polymer precursor is metered into the open mold in the amountat which the edge of the surface of the liquid precursor contacting theinner surface of the open mold is located under the peripheral circularsharp edge of the open mold or reaches this peripheral circular sharpedge and at least a part of the surface of the liquid polymer precursorwill protrude above the plane defined by the peripheral circular sharpedge of the open mold, or at least a part of the surface of the liquidprecursor lies in this plane or the whole surface of the liquid polymerprecursor lies below this plane, while in this case the liquid polymerprecursor will be metered into the open mold in the amount, which willalways be higher than the amount of the liquid polymer precursor neededto obtain a contact eye lens of the same diameter, b) then the openmold, which contains the liquid polymer precursor, is rotated around itsvertical axis at a speed at which the edge of the surface of the liquidpolymer precursor reaches the peripheral circular sharp edge of the openmold, the liquid polymer precursor is in contact with the whole innersurface of the open mold and the surface of the liquid polymer precursoris located in the plane defined by the peripheral circular sharp edge,or is located above or below this plane, c) the liquid polymer precursoris exposed to solidifying conditions, under which it will be able oftransformation into a state of a clear, solid polymer by polymerizationand/or cross-linking; d) and the open mold continues to be rotated underthe said solidifying conditions at the said speed at least until thetime, when the edge of the surface of the polymerized and/orcross-linked liquid polymer precursor reaches the peripheral circularsharp edge of the open mold even if the rotation of the mold was sloweddown or stopped; e) then the rotation of the open mold is optionallyslowed down or stopped f) and the exposure of the contents of the openform to the said solidifying conditions continues at least until thesaid transition is attained, g) whereupon the implantable lens isremoved from the open mold.
 24. A method according to claim 23, whereinthe liquid polymer precursor contains at least one monomer with at leastone double bond polymerizable by free-radical polymerization.
 25. Amethod according to claim 24, wherein the free-radical polymerization isinitiated by the fission of an initiator containing a peroxide bond oran azo-bond.
 26. A method according to claim 24, wherein thefree-radical polymerization is initiated by free radicals formed by theaction of radioactive or electromagnetic radiation or by the action ofaccelerated electrons.
 27. A method according to claim 24, wherein themonomers with at least one double bond polymerizable by free radicalscomprise derivatives of acrylic and/or methacrylic acid.
 28. A methodaccording to claim 27, wherein at least one of the derivatives ofacrylic and/or methacrylic acid is an ester of a polyhydric compoundwith at least two molecules of acrylic and/or methacrylic acid.
 29. Amethod according to claim 27, wherein at least one of the derivatives ofacrylic and/or methacrylic acid is a salt of the acrylic or methacrylicacid.
 30. A method according to claim 24, wherein at least one of themonomers with at least one double bond polymerizable by radicalpolymerization contains a functional group capable of absorbingelectromagnetic radiation in the range between 190 and 500 nm,advantageously between 300 and 400 nm.
 31. A method according to claim30, wherein the functional group capable of absorbing electromagneticradiation is derived from benzophenone or benztriazole.
 32. A one-pieceopen mold for the execution of the method according to claim 23, whereinit comprises an open concave cavity, delineated by a functional shapinginner surface ending by a peripheral sharp edge having the shape of acircle which lies in the plane perpendicular to the vertical axis of theopen concave cavity and has a diameter of 5 to 10 mm, which open concavecavity passes in the top part of the open mold over an intermediatecircular edge having the shape of a circle lying in the plane parallelto the plane of the peripheral circular sharp edge, into a transitionalopen cylindrical or frustum-of-a-cone cavity delineated between theperipheral circular sharp edge and the intermediate circular edge, andthe functional shaping inner surface of the open concave cavity has theshape defined by the rotation of a part of a conical section along thevertical axis of the open concave cavity, the conical section beingdefined by the equation Y=−a+(a/b)*(b²+X²)^(0.5), in whicha=R_(c)·(1+h)² and b=R_(c)·(1+h), where R_(c) is the center curvatureradius and h is the parameter defining asphericity, which is selectedfrom an interval between −0.75 and +1
 33. An open mold according toclaim 32, wherein the center curvature radius R_(c) is chosen from aninterval from 2 to 20 mm, advantageously from 2.5 to 5 mm.
 34. An openmold according to claim 32, wherein the peripheral circular sharp edgehas the shape of a circle with diameter from 7 to 9 mm.
 35. An open moldaccording to claim 32, wherein the height of the transitional opencylindrical or frustum-of-a-cone cavity is equal to 0.01 to 0.2 mm,advantageously 0.03 to 0.08 mm.
 36. An open mold according to claim 32,wherein the volume of the open concave cavity, or optionally thecombined volume of the open concave cavity and the transitional opencylindrical or frustum-of-a-cone cavity, equals 15 to 175 μl,advantageously 25 to 55 μl.
 37. An open mold according to claim 32,wherein it is formed from a polymeric plastic which is not wettable, oris only incompletely wettable by the liquid polymer precursor.
 38. Anopen mold according to claim 37, wherein the said polymeric plastic is apolyolefin.
 39. A method according to claim 25, wherein the monomerswith at least one double bond polymerizable by free radicals comprisederivatives of acrylic and/or methacrylic acid.
 40. A method accordingto claim 26, wherein the monomers with at least one double bondpolymerizable by free radicals comprise derivatives of acrylic and/ormethacrylic acid.